Program: GN-2016B-Q-24

We propose to obtain long-slit optical spectroscopy on prominent tidal features located in two interacting galaxy groups using GMOS-N. AGC 208457 is a probable tidal dwarf galaxy (TDG) located in the NGC 3166/9 group. Recent neutral hydrogen (HI) observations and deep optical photometry show that this feature has several hallmark characteristics of a genuine TDG, however, the lack of optical redshift and metallicity estimates makes definitive classification elusive. NGC 4747 has a tidal tail that appears to contain two HI peaks and two star clusters. Nevertheless, spatial offsets between the peaks and clusters, asymmetry of the gas from the stellar tail, as well as an arching ultraviolet stream complicate the geometry of the tail. High quality spectroscopic observations would confirm the radial velocity of key stellar objects, could verify their physical association with the gaseous component of each tidal feature, and will help disentangle any projection effects. Emission line flux ratios would be used to compute chemical abundances and estimate the gas-phase metallicity, which could verify tidal origins, thereby increasing the detection rate of TDGs and furthering the understanding of their significance in galaxy evolution.